A common means of exchanging heat energy between two fluids is to drive the first fluid through a highly thermally conductive pipe or tube and to flow the second fluid across the outside of the tube. Specific applications include industrial and automotive heating and cooling equipment such as air conditioners.
Flat-oval tubing has proved a very effective thermally conductive pipe for carrying the first fluid in such applications. The surface with which a specific volume of fluid thermally interacts while flowing through a pipe or tubing is increased by using flattened tubing rather than round tubing and further increased by placing transverse webs of a highly thermally conductive material across the tubing.
Aluminum is used extensively in such applications because of its relative cost, its high thermal conductivity and the ease with which aluminum tubing is fabricated. The ductile nature of this metal is further an important attribute in many applications in that it permits easy construction with prefabricated tubing that it is easily bent and retains the desired shape once bent.
The method of the present invention relates to a method for reforming a fixture receiving end of flat-oval tubing of the kind described above which is divided by transverse webs into separate chambered conduits that extend the length of the tubing.
However, flat-oval tubing which is desirable for the heat transfer characteristics is difficult to work with because standard fixtures and equipment that are readily available on the market fit only round tubing. Placement of valves and connections both entering and leaving the heat exchange tubing is awkward and is severely limited by the commercially available options. Adapters which fit at one end onto the flat-oval tubing and present a standard round configuration on the other end are difficult to seal about the tubing and adversely affect the flow within the tubing.
It is an object of the present invention to provide an efficient method for reforming a fixture receiving end of flat-oval tubing into a round configuration to provide for secure, sealed interface with the readily available standard fixtures designed for round pipe. It is another object of the present invention to minimize stress concentration and maximize fluid flow characeristics for heat transfer in the transition from round conduit to the flat, oval heat exchanging tubing having integral transverse webs.